Your question does not have a simple answer. Many things come into play such as engine size, compression, head design, gear ratio's, how well your engine compartment is sealed. Do you have auxillary air holes with ducted air to allow cool air to the fan. Do you have an external oil filter, external fan and oil cooler in conjunction with a dog house oil cooler, do you have the Type IV oil cooler upgrade, how heavy is your right foot, is your fan belt adjusted properly, what size oil pump and manufacturer? Do you have an oil sump, what brand and weight of oil are you using, do you have a cylinder head temp gauge and an accurate oil temp gauge, as you can see, the list goes on and on.
For the most part, if you have a mildly built Type 1 engine, 90 degree weather is not a problem.
Think in these terms, a stone stock VW weighs much more than a Speedster and as such, the engine has to really work to propel the vehicle.
I remember during the summer of 1968 driving my stock Karmann Ghia from California to Florida in extremly hot weather at 80 MPH the whole way with no problems.
Larger engines, produce more heat but with the right equipment, 90 degree weather should be OK. Some engines not properly outfitted can stand only 80 degree outside air temp.
As I said, a lot more comes into play than just the weather.
By the way, here in Ontario, Calif (approx 40 miles east of Los Angeles) the weather has been in the 100's every day with a high of 105 on a few days. (I may as well be living in Arizona with this kind of heat)
In closing, how do you pronounce EH with a southern accent?
